We plan to define precisely biologically and chemically the region on the homogeneous human erythrocyte T antigen involved in breast carcinoma-characteristic cellular immune reactions. We have cleaved off such an active structure from T antigen. The active structure will be compared with corresponding structures we are isolating from breast cancer cell membranes. In vitro cell-mediated immunity response to T antigen and standard chemical, immunochemical and physical procedures will be used for this. For this purpose, we will isolate cell membranes and cytoplasm from large quantities of breast cancer tissue as well as benign and healthy breast tissue obtained at surgery. We will also isolate these cell components from tissue cultures of breast carcinoma cells and, in addition, study tissue culture supernatants since breast carcinoma cells shed T-, Tn-, and M-\and N-like substances into their environment. We will extract from these tissues glycoprotein and glycolipid fractions. From these we will isolate T-\and Tn-\and M-\and N-specific glycopeptides and glycolipids.